The median nerve is the nerve that runs through the carpal tunnel of the wrist and connects with the thumb and all fingers of the hand, with the exception of the little finger. This nerve originates with the cervical spine and is routed through the arm and forearm. The nerve gathers in compressed form to run through the narrow carpal tunnel and to the fingers. In addition to controlling sensation in the hand, it is also important to the general nerve function of the upper portion of the arm.
In relation to the hand, the median nerve controls all sensation and nerve function on the palm side of the thumb. The nerve also manages the process of sensation for the index and middle fingers, and half of the ring finger. For these three fingers and the thumb, the nerve also provide sensation for the nail bed on each appendage.
An injury to this nerve can occur in several different ways. Trauma at some point above the elbow will, in turn, inhibit the function of the lower limb, including the fingers of the hand. When there is compression or entrapment at some point in the forearm, this leads to a deadening effect commonly known as pronator teres syndrome.
One of the most common examples of median nerve damage is known as carpal tunnel syndrome. This disorder will develop when there is an unusual amount of compression in the carpal tunnel of the wrist. This leads to tingling and possible a complete loss of sensation in the thumb and first three fingers. At the same time, some people experience a great deal of pain when attempting to move the wrist. Depending on the severity of the compression, surgery may be required to correct the problem.
Other factors can create situations where the nerve is compressed or squeezed, effectively limiting the function. Inflammation of muscles due to infection or trauma can interfere with the proper function of the nerve. Surgery on the arm may also temporarily affect nerve function, causing various points along the arm or hand to have a tingling sensation or have no sensation at all. Normally, as the body recovers from the surgery or inflammation, normal sensation will return. Tests can be used to determine the degree of damage sustained by the median nerve at any point between the cervical spine and the point of termination in the fingers of the hand.